Electric coil



Feb. 22, 1944. J DOELKER 2,342,532

" ELECTRIC COIL Original Filed May 22, 1941 William I. Doelker Inventor His Attorney Patented Feb. 22, 1944 re ies OFFiQiZ snsc'mrc COIL William J. Boelker, Dayton, Ohio, assignor to The National Cash Register Company,

Dayton,

Ohio, a corporation of Maryland Original application May 22, 1941, Serial No. 394,692, now Patent No. 2,320,573, dated June 1,

1943. Divided and this 1942, Serial No. 440.908

application April 29,

3 Claims. ('01. 219-13) This invention relates to an electric coil for use in the induction heating oi. the cutting lands of an external screw thread cutting die.

This is a division of applicants co-pending application for United States Letters Patent, Serial No. 394,692, filed May 22, 1941, which application issued into Patent No. 2,320,573, on June 1, 1943.

in hardening by heat treating the thread cutting parts of such a die, commonly termed a button die, trouble has heretofore been encountered, inasmuch as it has been necessary, in order to heat the lands, to heat the whole die, with a consequence that the heavy periphery thereof had a tendency to warp and cause the cutting surfaces of the die to move out of alinement.

This invention discloses a means for quickly heating the lands of such a die without materiallr' heating the periphery thereof, high frequency induction heating being employed, using a special coil particularly shaped to be entered into and positioned properly within the clearance holes of the die so that the lands lie with n the coil.

Therefore, it is the principal object of this invention to provide a means for the hardening 4 of the lands of an external screw thread cutting die by means of high frequency induction heati s.

Another object of the invention is to provide an induction heating coil particularly adapte to heating the lands or an external screw thread cutting die without heating the periphery of the die.

With these and incidental objects in view, the invention includes certain novel features, the essential elements of which are set forth in appended claims and a preferred form or einloodi:

merit of which is hereinafter described with reference to the drawing which accompanies, and forms a part of this specification.

In the drawing:

Fig. l is a perspective view of a typical button type external thread cutting die with the novel high frequency induction heating coil in place for the heating of the lands.

Fig. 2 represents a section through the coil of Fig. 1 above the die and on a plane perpendicular to the axis oi the die.

The button die illustrated in Fig. 1 is typical of those used for cutting external threads on screws and consists of a periphery l9, iour inwardly extending lands II having cutting surfaces on their inner ends, and four clearance holes [2 intermediate the lands.

The clearance holes I! aflord room for the insertion of the novel induction heating coil is, formed or two turns of hollow electric conducting tubing, the coils being so wound in a helical spiral, preferably flattened laterally as shown, that two or the clearance holes l2 diametrically opposite can be utilized to accommodate said. coils in the manner shown in Fig. 1,-the thread cutting portions oi the lands thereby being disposed within the internal heat zone of the coil, said internal zone of the coil being energized to a much greater degree than the exterhal zone of the coil, thus causing a great differential between the applied heat on the lands and heat on the'periphery.

It is to he noted that one of the turns of the coil, having a greater long diameter than the other turn, permits the two turns of the coil. to be manipulated by compression and side displacement of adjacent turns of the coil, one side a time, so as to be insertable into the associated clearance holes by way of the passages it (Fig. 2). The coil, by its natural resilience, returns to normal shape after the manipulation and is therefore disposed within the clearance slots as best illustrated in Fig. 2, wherein it is shown that the turns of the coil do not touch one another or the lands of the die, but are positioned sym metrically in relation thereto. By the above de scribed method of inserting the elongated cell, it is so positioned that four of the lands equally within the internal heating zone of the coils and receive equal and in tense as compared with the periphery of the die, which is relatively distantly located in the outer heating field oi the coil, thus resulting in concentrating the heating effect of the coil on the lands and particularly on inner ends thereof.

After the coil is inserted as shown, a high ire" quency current is passed through the coils tor the required time according to the kind of metal, the size of the die, and other factors necessary to consider to secure proper induction heating. After the required heating is accomplished, the current is shut off, the die is'quenched by water or other cooling agent, and the coil is removed by reversing the movements by which it was insorted.

By the above described means, the thread cutting parts of the die are hardened, and the periphery of the die is left in its original shape and toughness without warping or misalining the cutting lands.

The coils may be made of the diameter of tubing and of the proper tightness of coiling as best ance holes.

and described are admirably adapted to fulfill the objects primarily stated, the invention is not to be limited to the form or embodiment herein disclosed for it is susceptible of embodiment in various forms all coming within the scope of the claims which follow.

What is claimed is: I

1. An electric coil comprising two elongated parallel loops, each loop located in a separate plane and. interconnected at one end 'by an oblique section, the ends opposite the interconnected ends of said loops being formed with the l5 2,342,532 ,suitthe size of the die and the size of the clear- 2. An electric coil comprising tour parallel sections connected in oflset pairs to form two elongated loops each related pair occupying one of two difierent parallel planes, the length of one related pair of said sections being'longer than the length of the other related pair'of secticns, and

the bight or one loop extending beyond the bight or the other loop.

3. An electric coil comprising two elongated loops, the elongated sides of the loops forming four parallel sections with the related sections of the loops located in different parallel planes, and the sections of one'loop being longer than the sections of the other lop.

WILLIAM J DOEIKER. 

